# isIntersecting: Determine Whether Polygons are Self-Intersecting In PBSmapping: Mapping Fisheries Data and Spatial Analysis Tools

## Description

Determine whether polygons found in a PolySet are self-intersecting.

## Usage

 `1` ```isIntersecting (polys, numericResult = FALSE) ```

## Arguments

 `polys` PolySet to use. `numericResult` Boolean value; if `TRUE`, returns the number of intersections.

## Details

When `numericResult = TRUE`, this function counts intersections as the algorithm processes them. It counts certain types (i.e., those involving vertices and those where an edge retraces over an edge) more than once.

The function does not give special consideration to holes. It returns a value for each unique (`PID`, `SID`), regardless of whether a contour represents a hole.

## Value

PolyData with columns `PID`, `SID` (may be missing), and `intersecting`. If `numericResult` is `TRUE`, `intersecting` contains the number of intersections. Otherwise, it contains a Boolean value.

## Author(s)

Nicholas M. Boers, Associate Professor – Computer Science
MacEwan University, Edmonton AB
Last modified `Rd: 2013-04-10`

## See Also

`isConvex`, PolySet.

## Examples

 ```1 2 3 4 5 6 7 8``` ```local(envir=.PBSmapEnv,expr={ #--- load the data (if using R) if (!is.null(version\$language) && (version\$language=="R")) data(nepacLL,envir=.PBSmapEnv) #--- calculate then print the polygons that are self-intersecting p <- isIntersecting(nepacLL, numericResult = FALSE) print(p[p\$intersecting,]) }) ```

PBSmapping documentation built on Jan. 15, 2021, 3:41 p.m.